1. Field of the Invention
This invention pertains to electrical service conduits extending from buried or underground service lines to individual electrical service installations comprised of buildings requiring power and more particularly to providing means for protection of the building electric service from damage and possible interruption as a result of ground subsidence or other disturbance in the area of the underground electrical service lines. More particularly still the invention pertains to a slack provision arrangement to provide additional service cable to allow for any additional length of service line necessary to relieve tension on the service attached to a building induced by ground level alterations.
2. Preliminary Discussion
In the connection of underground electric service to building structures, difficulty has been encountered with settling of backfill over buried electrical conduits on building sites. It is not unusual for such backfill to settle several feet or more along with the conduits surrounding the service. Such settlement can initially be at a fairly high rate of several inches or more per month particularly during periods of high rainfall. The force of such settlement is transferred to the conduit and the electrical service wires where they are connected to the electrical service box on the exterior of the building. Even if the service wires are not broken or disconnected by the resulting tension exerted on them, sections of the protective conduit around the service wires are frequently pulled apart or away from each other or from the service box, exposing the service wires and sometimes even pulling the building service box away from its anchoring or even breaking away portions of the building structure to which the service extends. Exposure of the service conduit or wires is not only dangerous because of the danger of severe shock by anyone coming in contact with the service wires or conduit, but constitutes a fire hazard due to possible ignition of surrounding materials in case of breaking and exposure of the wires.
This problem was recognized in U.S. Pat. No. 4,981,942 issued to T. F. Moran, Jr. on Aug. 29, 1989, entitled “Adjustable Riser Assembly”, which discloses an adjustable length conduit for protecting underground electrical power service wires between the ground and an exterior above ground service box. Such prior art riser assembly is comprised of a first lower conduit section the lower end of which extends into the ground and has a bend of at least 30° on such end, and a second rigid conduit which connects to the service box on one end and has a larger overall diameter along its lower end so as to slidingly receive the upper end of the lower conduit section. A very close tolerance is provided between the outer diameter of the lower conduit section and the inner diameter of the upper conduit section, with such diameters being substantially the same so that at least partial sealing between the two diameter conduits is effected. The two conduits overlap and allow for subsidence of the ground surface in new construction while maintaining a substantially sealed conduit protection of the electrical service wires between the service box and the ground. Such continued protection is important not only to prevent children or others from gaining access to and possible experiencing injury from the charged service wires, but also to keep insects and small animals out of the service box and building and to prevent the service box in an extreme but not uncommon case from being bodily ripped from its position on the wall. The Moran Jr. invention therefore addressed a very serious consequence of backfill settlement in building construction.
There are several problems, however, with the Moran, Jr. riser protection assembly which make it in practice impractical and difficult to use and install. First, the close sliding fitting or tolerance between the conduits does not allow for any lateral or side to side movement of the lower conduit with respect to the upper conduit. Thus, if the lower conduit is not installed so that it is exactly aligned with the upper conduit, the outer edge of the lower conduit will press against the inner side of the upper conduit and will not slide easily or possibly even at all due to frictional forces between the conduits. This makes the Moran, Jr. protective assembly very difficult to hook up, or install, since, in most cases, it is difficult and time consuming to install the conduits so that they are exactly aligned. Furthermore, just as settling forces may cause downward strain on a nonadjustable conduit, such forces may also place significant lateral pressure on the below ground portion of the adjustable conduit which may in itself exert sufficient force to loosen the conduit from the wall. Yet another problem with the Moran, Jr. assembly is that if the upper slightly larger conduit and the lower smaller conduit are not exactly aligned, when the smaller enters into the larger it can be inserted only a minimal distance before its edge begins to severely impact the inside of the larger pipe and refuses to slide farther without displacing the larger conduit which may be already secured to the wall when the electric lines are installed. Consequently, the lower small conduit is extremely difficult to install or insert into the larger upper conduit again primarily due to the close fit or tolerance between the upper and lower conduits.
The present inventor recognized the disadvantages of known sliding or slip joint type devices, and conceived of a new assembly that overcomes all of such disadvantages. In particular, the present inventor solved the problem of the lateral stress placed on the sliding portions of the conduits by using a larger inside diameter conduit assembly or fitting as the outer conduit plus placing a deformable sealing ring at the end of such fitting between the conduits. The deformable sealing ring is secured to the inner diameter on the lower end of the assembly, so that the section of conduit that extends into the ground will connect with such assembly with a close fit between it and the sealing ring, rather than with the inner diameter of the assembly or fitting itself. The improved slip-joint provided is described and claimed in applicant's prior application Ser. No. 11/098,860.
In addition, the prior patented invention did not address the possibility that subsidence of the ground or backfill might stress the underground electrical service conductor or cable itself and possibly pull it loose from its connections and the present inventor therefore provided an improvement in the basic sliding coupling in the top to provide an additional length of wire conduit to allow for slack therein to allow for the extra conduit that may be necessary to provide a continuous length of cable between the service connection and the power line connection at the street in case of settlement with additional inevitable lengthening of the path which a cable must follow in its path from a service box on a building to a service connection at the street. This allowed additional service cable to be paid out from the storage in the upper portion of the connecting slide fitting to allow for the lengthening of the conduit and tension of the electric cable itself.
However, it has now been found that providing a slack reservoir in the upper end of the slide fitting providing additional extension for the conduit attached to the building may not always be sufficient and that a more easily paid out length of excess cable may be desirable more in line with the underground section of the main run underground of the cable from the building to the street service. The present applicant has supplied such a slack arrangement in accordance with the present invention by providing a slack receptacle or container adapted to contain an underground loop or loops of electrical conduit which are automatically paid out upon the application of tension upon the electric cable caused by subsidence of backfill or the like. The container or receptacle may be constructed of polyvinylchloride, the approved material for service cable conduits because of its weather resistance and fire resistance in case the wires or electrical conduit is short-circuited in contact with it. However, sine there is little danger of fire underground, other structural plastics may be used. The slack cable or conduit within the receptacle or box is easily available and is placed in the receptacle through a door or cover and will be adapted to contain at least one full loop of wire, cable or conduit arranged to be easily paid out in either direction from the receptacle in case of need due to subsidence or any other severe tension on the electrical service. Since the receptacle is buried or arranged in line with the electrical service it is arranged to easily pay out cable or conduit in either or both directions upon tension being exerted upon the cable tension loop within, thereby preventing any accumulation of tension, due especially to subsidence, from tensioning the electrical service box or the service to the street and possibly detaching or breaking the wires or even pulling the entire service from the wall of the building to which it is connected. The slack receptacle should be strong enough to withstand the weight of earth over it, plus the possible weight of machinery and vehicles passing over the surface of the earth fill over it and is preferably at least somewhat impervious to the silt laden water percolating around it. While moisture entering the slack receptacle will not usually be deleterious to the electrical conduit or cable, which is designed for underground service in any event, the collection of silt within the slack receptacle can cause any cable loop therein to become substantially immobile and prevent it from being able to pass the slack in the cable from the receptacle. See, however, the further discussion hereinafter.
The usual underground cable run will be provided on the sides and preferably the top with so-called “screening” in the form of a layer of small broken rock to protect the cable and conduit from deleterious underground movements and influences including mud and silt flows. However, such screening may not be sufficient to prevent the passage of very fine silt particles. While larger clastic or divided materials will be excluded by such broken rock screening, fine silt and the like may still percolate through the screen and upon entrance in the slack receptacle settle in the center of a coil of wire or cable and possibly effectively resist the contraction of said coil or cable, thereby resisting payout of the coil and the relief of tension caused by earth subsidence. This, however, depends also upon how much flow of moisture is likely to occur through the slack chamber and if the chamber is carefully designed to limit such flow no serious consequences may result.
The primary focus of this invention, therefore, is the provision of a sturdy damage proof containment suitable for the containment of at least and in fact preferably one large loop of electrical service wire from which wire or service cable can be paid out simply and reliably to provide extra slack to prevent serious electrical service tension on a wire service and into which containment means the electrical service cable can be conveniently strung when installing the electrical service. It is preferred as noted above that only a single large loop be used.
Several embodiments of the invention can be used dependent upon the local utility custom respecting the laying of conduit to the street service, i.e. whether conduit is laid only from underground upwardly to the building service with the remainder of the run to the street service being without conduit protection, this being referred to as direct burial or whether protective conduit surrounds the electrical cable all the way to the street service referred to as non-direct burial.
3. Description of Related Art
U.S. Pat. No. 4,006,289 issued to N. P. Roe et al. on Feb. 1, 1977, entitled “Electromechanical Cable Deployable in a No-Torque Condition, and Method,” discloses a method and means for winding cable torque free in a coil placing one full twist in the coil with each winding so that when removing the cable from the coil it is presented without twist. The cable can be wound on a reel or into an open container. There appears to be no disclosure of the coil as a supply of cable for pay out to relieve tension, however.
U.S. Pat. No. 4,579,403 issued to N. R. Bryne on Apr. 1, 1986, entitled “Electrical Junction Assembly with Adjustable Connectors,” discloses in FIGS. 3 through 8 a slack cable containing chamber for paying out extra cable to be used in revamping of office furniture arrangements rather than having to install all new wiring. The structure actually shown would appear to provide only a relatively small amount of slack cable and the structure while appearing fairly sturdy, is not intended at all for underground usage.
U.S. Pat. No. 4,864,080 issued to H. P. Fochler et al. on Sep. 5, 1989, entitled “Terminator Connector Fitting for Electrical Box and Conduit System,” broadly discloses the use of a connector box for electrical fitting, but does not disclose an arrangement for coiling extra cable in a fitting below ground level to provide slack to relieve tension on the cable in the case of ground subsidence.
U.S. Pat. No. 4,844,863 issued to R. A. Throckmorton on Dec. 5, 1989, entitled “Optical Fiber Splicing Enclosure for Installation in Pedestals,” discloses an improvement in copper chambers sometimes used in former times to provide excess communication cable at the surface or above ground level to allow for splicing of new communication lines. The Throckmorton invention adopts such above ground structures by incorporating a curved holder for storing fiber optic cable with curvatures greater than the so-called critical bend radius beyond which the walls of fiber optic cable will not transmit electromagnetic radiation.
U.S. Pat. No. 6,031,180 issued to R. J. Schilling et al. on Feb. 29, 2000, entitled “Below Ground Pressurizable Cable Interconnect Enclosure,” discloses a specialized below ground interconnect chamber for electrical cable. The chamber is formed from plasticized concrete and is provided with internal environmental gases and is attached to PVC conduit. The cable connection chamber is designed to be useful for various interconnect purposes.
U.S. Pat. No. 6,181,861 issued to W. Wenski et al. on Jan. 30, 2001, entitled “Arrangement for Branching a Telecommunications Cable Containing Several Stranded Elements with Optical Fibers,” discloses a below ground chamber in which a number of fiberoptic cables can be stored in individual plastic cassettes or tubes and from which when a new connection to a local customer is to be made one or more of the fiberoptic cables or strands can be paid out to the customer from coiled fiberoptic strands stored in cassettes in the below ground chamber.
U.S. Pat. No. 6,526,858 issued to K. J. Smith et al. on Mar. 4, 2003, entitled “Cable Breakaway Assembly,” discloses an alternative way of preventing excessive tension on communication lines including a knife severing arrangement to sever the lines when excessive tension on a line occurs.
U.S. Pat. No. 6,646,854 issued to W. J. Fowler et al. on Nov. 11, 2003, entitled “Lightning Suppression Attenuator and System Employing Same,” discloses an underground container in which a conductive strand is coiled surrounded by conductive grit. Preferably the chamber outside the coil is filled with a conductive steel grit. The interior of the chamber, being surrounded by conductive grit to draw off any charge from a lightening strike, the cable within is neither intended to nor would it be able to pay out any substantial amount of slack cable in case tension was applied to the cable.
U.S. Published Application No. 2002/0034369 on Mar. 21, 2002 to J. H. Forrester et al., entitled “Apparatus for Storing Surplus ADSS Cable,” which is a CIP of several earlier applications previously issued discloses an adaptation of a presently popular arrangement for providing slack which can be paid out in overhead lines when required. The arrangement is designed for use in overhead lines and not for relieving tension on underground lines.
U.S. Published Application No. 2002/0172489 on Nov. 21, 2002 in the name of B. H. Daoud et al. entitled, “Fiber Splice Holder with Protected Slack Storage Feature,” discloses a fiberoptic splice holder with a slack storage feature. The application explains that in fiber splice holders which keep various spliced fiberoptic fibers separated and prevent the fiberoptic element from being bent at too great an angle it is convenient to have slack provided right on the splice holder.
U.S. Published Application No. 2003/0123935 on Jul. 3, 2003 in the name of D. Dofher entitled, “Subsurface Fibre Optic Cable Network Installation,” discloses a small junction box for fibre optic cable with at least one separable sidewall and sealing means for fibre optic cable entering from the side. The junction box is designed to fit into narrow subsurface openings. A wire loop may be on the outside to hold further loops of fibre optic cable.
Patent document EP0726478 to G. S. Cobb et al. published Aug. 14, 1996, entitled “Splice Holder Assembly for an Optical Fiber Cable Splice Closure,” discloses a splice holder for a fiber optic cable in which slack loops of fiber optic cable can be loops in the bottom.
None of the prior art known to the applicant discloses a slack cable box or case adapted to be used in the manner of that of the present invention for containing electric service cable looped in a loose coil in a slack coil container adapted for burying at the end of an underground conduit and to provide cable slack in the event of ground or fill subsidence, which cable slack will allow for such ground subsidence and prevent severe tension from being applied to exterior service facilities on the wall of a building and further deigned to have cable simply and easily coiled manually into the slack container by personal laying the conduit in place.